Since their discovery in 1985, fullerenes (C60 or buckyballs) have been among the most widely studied and used carbon-based nanomaterials due to their unique structural and electronic properties that enable numerous industrial, electrical and medical applications. However, the low solubility of these carbon-based nanomaterials in aqueous solutions restricts their use in this medium, stimulating research directed to their dispersion in aqueous solutions. For example, the water solubility of fullerenes can be improved by coupling the fullerene cage with hydrophilic molecules, forming functionalized fullerenes. One example of functionalized fullerenes is polyhydroxy fullerenes (PHFs, also named fullerols or fullerenols) wherein the fullerenes are functionalized with 1 to 48 hydroxyl groups per molecule.
One advantage of functionalized fullerenes is that they reduce oxidative stress by scavenging reactive oxygen species (Chen et al., Fullerene Derivatives Protect Against Oxidative Stress in RAW 264.7 Cells and Iischemia-Reperfused Lungs, Am. J. Physiol. Regul. Integr. Comp. Physiol., 2004, 287(1), R21-R26; Injac et al., Protective Effects of Fullerenol C60(OH)24 Against Doxorubicin-Induced Cardiotoxicity and Hepatotoxicity in Rats with Colorectal Cancer, Biomaterials, 2009, 30(6), 1184-1196) and have been examined for their antioxidant applications. Furthermore, fullerenes have been disclosed as therapeutics (Chiang et al., U.S. Pat. No. 5,994,410) and for use in cosmetics (Takada et al., European Patent Application Publication No. EP1894973). Some studies indicate that e,e,e-C60(C(CO2H)2)3 may extend the lifespan of mice (Quick et al., A Carboxyfullerene SOD Mimetic Improves Cognition and Extends the Lifespan of Mice, Neurobiology of Aging, 2008, 29(1), 117-128) and injected amphiphilic fullerenes ((H23C11CO2)2CC60C(CO2CH2CO2H)2) may stimulate hair growth in mice (Zhou et al., Fullerene Nanomaterials Potentiate Hair Growth, Nanomed. Nanotechnol. Biol. Med., 2009, 5(2), 202-207; Zhou et al., U.S. Patent Application Publication 2008/0213324 and Keply et al., WO/2009/114089). However, no reproductive effect of functionalized fullerenes has been observed so far.
As the global production of fullerenes and their derivatives is rapidly growing, fullerene containing products will inevitably enter various environments during their production, use and disposal. Among these environments, aquatic systems are probably the primary sink for carbon-based nanomaterials (Lyon et al., Implications and Potential Applications of Bactericidal Fullerene Water Suspensions: Effect of NC60 Concentration, Exposure Conditions and Shelf Life, Water Sci. & Technol., 2008, 57(10), 1533-1538; Gao et al. Dispersion and Toxicity of Selected Manufactured Nanomaterials in Natural River Water Samples: Effects of Water Chemical Composition, Environ. Sci. & Technol., 2009, 43(9), 3322-3328). Therefore, it is critical to identify the potential impact of this nanomaterial in an ecological system and, where possible, to positively exploit their introduction into a controlled environment.